The U.S. is currently a mixed economy. It is not, at least in the strict definition of the term, a socialist economy.Socialism must eventually cause ruin.
Detroit offers some lessons related to the depletion of human capital (population decline + departure of highly educated persons + failure of schools to regenerate human capital) in which the environment became inhospitable to economic activity, that decline in economic activity fueled significant socioeconomic problems, public finances deteriorated to the point where basic services were no longer provided effectively, all of which further compounded Detroit's problems.Detroit lets us stare our fate in the face.
The U.S. as a whole does not face such a dire problem anytime soon. It does risk a continued erosion of its competitiveness on account of the stagnation of its educational attainment and emergent gap with OECD countries. Some of this gap is already being reflected in early indications that the rate of U.S. innovation is slowing, which means diminished long-run growth potential. The U.S. still has broad flexibility to address its major problems, as well as the capacity to make necessary investments. Hence, a decline is not inevitable. There is an alternative path. However, a continuation of political dysfunction will plant the U.S. on a less than optimal path, as the changing world requires more than the status quo (the default policy from political dysfunction).